The present invention relates to improvements in destaticized driving belts.
Driving belts such as V-belts and timing belts are normally manufactured from rubber or high polymer compounds. When such a belt is being run, due to slippage on the pulleys on which it is run, the belt has a tendency to become charged with static electricity As a consequence, there is a danger of receiving a strong electric shock if the belt is touched.
There have heretofore been employed various techniques for preventing such a belt from being charged with electricity. These include the following: (1) conductive powder is adhesion-bonded to tension members, or metal foils are wound on their outer surfaces (Japanese Utility Model No. 18032/1975); (2) highly conductive woven fabrics are arranged on outer belt faces (Japanese Patent Laid-Open Pat. Appln. No. 63150/1981); and (3) carbon powder is applied to the belt sides, or members constituting the belt side face are made to contain carbon powder (Japanese Laid-Open Pat. Appln. No. 124563/1977).
However, those techniques have disadvantages.
These include, in the case of (1), an uncertain charging preventive effect due to variations in the coil pitch of the tension member, low adhesion between the tension member and the rubber, reduction of the life of the belt because of the low adhesion between the tension member and the rubber when metal foil is wound thereon, and difficulties in carrying out foil-winding operations and unsatisfactory results thereof; in the case of (2), i.e., coating outer layers with woven fabrics, problems related to the strength of woven fabrics and attendant high costs; and further, in the case of (3), a fast reduction in the conductive function resulting from scattering of carbon powder while the belt running.
On the other hand, use has been made of conductive powders such as carbon, graphite or copper in the form of powder blended with a rubber component of, for example, a compressed layer (14), as shown in FIG. 1. However, such use of conductive powder has been proved not only disadvantageous but also unsatisfactory in that the dispersion properties are reduced as the quantity of additive increases, and the mechanical properties of rubber are adversely affected. With respect to destaticization of a belt of this type, there is another disadvantage in that, although the conductive rubber layer functions properly as a destaticizer while the belt is new, the conductive rubber layer rapidly wears out and ultimately stops functioning as a destaticizer.
The difference in abrasion is mainly due the fact that the driving belt is composed of different rubber materials, whereby the conductive rubber forming the compressed rubber layer 14 wears faster than that of the tension layer 13 or the cushion rubber 12 of the tension member layer. As a consequence, the destaticizing function will be eliminated if the belt starts floating on the pulley and the flange and fails to come in contact with the belt.